1. Field of the Invention
The present invention relates to a sheet processing apparatus which stacks pieces of paper sequentially fed one by one, binds the center of the pieces of stacked paper, and folds the thus-bound set of paper in half.
2. Description of the Related Art
Some conventional copying machines or printers have a processing function for stapling plural pieces of stacked paper to form a set, binding the set of stapled sheets, and folding the center of the set of stapled sheets paper in half.
In such a copying machine or printer capable of effecting such a folding operation, pieces of paper are temporarily stored in a tray called a compiler tray for aligning paper which is an object of stapling. Subsequently, the sheets are transported to a stapling position for stapling the center of the paper. After having been stapled, the set of pieces of paper is transported to a folding position where the set is folded in half by means of the folding mechanism.
In such a copying machine or printer, the stapled position of the set of pieces of paper sometimes becomes deviated from the position of the folding line of the set of pieces of paper to be used for folding operation.
There is proposed inhibition of occurrence of a deviation by accurately transporting the pieces of paper to the stapling position from the compiler tray (refer to JP-A-2002-068518).
In the above-described proposal, it is known that, even when the center of paper is stapled, a deviation between the stapled position and a folded line becomes larger as the number of pieces of paper bound by the stapler is increased. This results in a problem of poor appearance.
The above-described problem arises not only when the recording paper whose center is bound is folded in two half, but also when center-bound sheet-like substances other than the recording paper are folded in half.